Introduction: Pinebox Portable Computer Case 1
As part of a larger project (a portable Raspberry PI computer), this is a design-and-build for a wooden box to contain the computer.
It's split into three instructables (although building of the three parts was done in parallel).
Part 1 is the outer box, Part 2 is the inner wooden framework for mounting the Pi and screen, and Part 3 is the lower woodwork for mounting the keyboard, batteries, and I/O port expansion.
No laser cutters or CNC machines were used in the making of this box!
Step 1: Parts List
Materials for all three parts of the case are shown here :-
- Pine Wood Strips (600mm x 25mm x 5mm) £18 for pack of 40 from eBay, (needs just over half of the pack).
- Dark Hardwood Strip (4mm thick, 22mm wide, about 800mm long) (1)
- Brassware -- Hinges (3), Clasps (2), Friction Stays (2)
- Supermagnets (10mmx5mm) (5)
- Optical Quality Glass (Microscope Slides 76mmx26mmx0.9mm) (2)
- Plastic diffuser material (ex-Camera Flash)
- IR Pass filter material (surplus item)
- Speaker Grilles (recovered from the cheap PC speakers used in project)
- Small aluminium/steel plate offcut
- CD Jewel case (for clear plastic material)
- Self adhesive felt/rubber feet (8)
- Self adhesive felt strips (4)
- Self adhesive felt pads 5-8mm dia (3)
- Various Screws, Pins, Bolts, Hex Threaded Bushes, Washers (sizes non critical/to suit, see text)
- PVA glue
- Rapid Araldite Epoxy
- Cyano Superglue
- Greaseproof/Parchment paper
- Silicone Sealant (glassware mounting/sealing)
- Isopropyl Alcohol (clean up of wood/glass)
- Rustin's Pine Woodstain
- Rustin's Plastic Clear Coating and Thinners
- Paint: Wood Primer, Undercoat (brushed)
- Paint: Matt Black (sprayed)
- Cellulose Clear Coat Lacquer (spray)
- Table Saw and Cross Cut/Mitre jig
- Minicraft/Dremel (and usual kit of drills, sanding drum/flats, shaped grinding stones, diamond tipped engraver, millers) and Mini Router jig
- Detail sander (e.g. Black And Decker Mouse)
- X-Acto Blades (Scalpel and chisel type)
- Approx 0.5" wide flat file
- Small needle files
- Right Angle square
- Clamps. Lots of them. And weights!
- Diamond scriber/glass cutter
- Steel rule
- Fine Grade Wet/Dry Paper
- Medium Sand Paper
- 0000 Wire Wool
- Polishing Wax
Step 2: Preparation
For the wood supplies, wider panels would have been simpler, but Wickes were constantly out of stock of the pine boards I wanted to use. eBay to the rescue.
Using the Blender design model, I created a rough cutting-guide layout to see how many pine sticks I would need. 19 sticks would be needed for making the outer case, so a pack of 20 wouldn't stretch. Pack of 40 it is then, leaving enough over for the other wooden parts inside.
From the pack of wood, I selected eight similar looking sticks to form the top and bottom boards, and then four other pairs to make the sides. Pay attention to which way the grain runs, to try and get matching pieces alongside each other, and to maintain the grain going around corners for a neater job.
These sticks had one side finished smoothly, and one side left slightly rough, so I arranged all the smooth sides "out" on the box.
Using a couple of the pine sticks and a flat board as a right-angle edge guide, and a lot of clamps, start gluing up the boards!
Gluing was done onto a layer of greaseproof paper (parchment paper) to stop the excess PVA glue sticking.
Fortunately these sticks were planed very straight and needed no further jointing/planing to square the faces up.
Step 3: Top and Bottom Boards
For the top and bottom boards, I clamped 3 sticks at a time (the limit of the clamps) into mini boards. For the remainder of the top, bottom (and the sides), they were clamped up in twos. 3+3+2 = 8 sticks wide for top and bottom.
Keep the "good" side upward so that glue squeeze out can be wiped away. The rough side (down) won't stick to the paper, but will have some squeeze out.
Once the boards are dry, I used a table saw jig to trim one edge dead square, and then measured and cut the two boards to size at 290mm. A further 48mm will be added shortly for a total size of 338mm wide.
Next I added "breadboard" ends. This hides the end-grain of the top and bottom boards, and protects them from damage. These are 24mm each, from one pine stick. Additionally I cut off and rotated the corners of these pieces at 45 degrees so that THEY don't have any visible end grain either.
The end grain is all hidden this way because it will look a lot darker when it comes to staining the box later. End-grain sucks up the stain in a way that the face of the wood doesn't.
I used some small 3/4" veneer pins, with the heads nipped off, to secure these ends in three places (each side), as well as PVA gluing them. Note: Avoid the locations where there will be a cutout later, for camera/flash windows etc.
I predrilled small holes for the pins, and tapped the wood into place -- clearing up any glue that squeezes out. Finally, put in the 45 degree corners, having checked that they don't show the end of the wood! Clamp it all up, put it between some flat, heavy surfaces, and wait.
The boards should match and be a little oversize for the sides to sit on. They will be trimmed and sanded back later, so oversize is good, and uneven edges is fine.
TOTAL BOARD SIZE when done = 338 x 196mm, which is about 3mm too long on each short end, and 6mm over on each long side due to natural width of pine sticks. It should be 332x184mm from Blender model. This leaves plenty of wiggle room when the sides go on.
When the glue is dry, pick the "best" board for the top, the other for the bottom. Mark them.
Step 4: Side Boards
The sides are made from pairs of pine sticks glued together as above. To make them into a box, all of the boards need to be bevelled (that's mitred, when stood up), again on a table saw
From the Blender model, the side lengths need to be 332x184mm outside dimensions. The widths of the pieces for the sides were left at 48mm, which is their "natural" size (two sticks).
Cut and bevel all the pieces to the correct lengths. Do all identical size pieces at the same time, with a stop block, so that they match exactly.
Keep track of which piece is which, to maintain the wood grain pattern around corners. neighbouring pieces of wood should end up next to each other on the finished box.
Rearrange the kit of wooden parts into the right order, and use Scotch tape or painter's tape on the outside of all the joints to check it makes a tight, square box. Lay the pieces out in a straight line, tape them, and the box should fold up into a square box with a LITTLE persuasion to close the last corner up.
Note: The piece marked up for the front-bottom-edge of the box needed 31mm cutting off (longitudinal cut/rip cut) to then re-stick it to the front-top-edge, to make a lip for the top of the box. See the "+ Extra" and "- Extra" comment on the images.
Step 5: Cutting/Milling Windows and Ports
This step is easier when the box is still flat!
Using the Blender model as a guide, mark in camera's "side" viewport into the right hand side, and the extent of the rebate for the glass (which goes inside the box). Cut them out with an x-acto "chisel" blade for neat edges, having milled out most of the waste with a dremel milling tool guide or similar.
The rear port will allow all the I/O connectors access to the outside world. To save alignment problems, and because some items are "unknown" at this stage, I've made this a plain square hole, which will be infilled later with a customised blanking plate. Again, cut this with an x-acto blade/steel rule and pop it out.
Step 6: Glue Up Sides
Now it should be safe to glue up the box.
End grain soaks up glue, and that leads to weak joints. So the first job here is to seal the ends. Brush on a mixture of equal parts PVA glue and water. Let it really soak into the ends, and then dry out for 2 hours.
Tape up the corners properly, by putting painter's tape/scotch tape on the outside of each corner, and butt the mitred points together. I'm assembling the top and the bottom at the same time here, to ensure they match, so I taped the top and bottom pieces crosswise too, to keep them together.
There is one critical area when gluing the box up: The overlaps between the top and bottom of the box. No glue must get in the area marked RED. The WHITE area is the bottom of the box (side and front), and the BLACK area is the top of the box (side and front). If glue gets on the RED area, the box will be permanently closed on one side.
So put a small amount of Scotch tape to exactly cover the RED zone, to stop it sticking. Do the same at the other end of these pieces of wood.
Also put tape along the edges of every mitre/bevel corner, on the inside flat face of the box, so that when glue squeezes out, it goes onto the tape, and is much easier to clean up.
Put glue into every bevelled corner. fold the box sides up, and tape the remaining corners together. It should now be square. I placed mine onto a flat surface, with a flat board on top, and put a weight on it, and left it overnight.
Step 7: Milling Logo/Windows Into Top
These jobs are also easier to do before the top goes onto the box!
Again we have windows (holes) and glass rebates on this piece. I marked the positions in from Blender model (and you can cross check this position with the "sides" if they are dry and fit to be handled).
The size of the window holes is set by the camera's view port -- see the Camera Spinner instructable. The size of the glass rebates needs to be larger, to match the glass pieces.
Cutting one of the microscope slides in half provides enough glass for two view ports.
Cutting the glass is fairly easy -- I scratched across the glass with a diamond scriber, using a steel rule as a guide.
Then, place the line in the glass over a small fulcrum point, like a piece of copper wire, to make a see- saw, and press down gently on both ends. The glass should snap cleanly across the line. I usually do this by feel, having covered it over with a piece of newspaper, to stop any flying glass shards.
Cut out the windows for the camera (and LIRC transmitter/receiver) with the X-acto chisel, then mill away a rebate deep enough for the glass.
For the marquetry logo I traced around the outside, and cut a rebate about 2mm deep almost to that line, using the milling cutter jig. Once this is done, you can use an x-acto blade to hand finish closer to the line, and then sand the base of the hole flat. Ish.
Step 8: Corner Splines
To strengthen the mitred corners, and because it looks nice, I added contrasting dark-wood splines to them.
The splines are simply triangular pieces of wood cut from a strip, as shown. They need to be large enough so that when the slots are cut into the box, they will overhang outside, ready to be cut/sanded flush.
Using the corner splining jig I put the slots into the corners of the box. Position is important, as one of them needs to co-incide with the bottom "lip" for the keyboard. So all positions were based off this key one.
It worked out that the all the slots needed to be 15mm from each side of the box to align correctly.
The splines (and some dark wood veneer shims) were glued into the corner slots, and then trimmed smooth with a makeshift "flush cut" saw.
This is a junior hacksaw blade, mounted BACKWARDS, so it cuts on the pull stroke. The handle is a couple of left over mitred bits of pine! It cuts very close without damaging the surface too much -- nothing that won't sand out later.
One of the splines is missing (not fitted) at each end of the keyboard, which will be fixed next.
Step 9: Catches, Hinges, Keyboard Spline
Next I marked in and temporarily attached the hinges for the lid, so that the thickness and fit of the keyboard "spline" and the top-lid-handle "spline" can be established.
The shape of these pieces is fiddly. It's cut from the same 20mm wood the splines were made from, but first split along it's length so that it's 10mm wide. It's cut slightly longer than the case is wide. Angles and positions need to be marked from the existing woodwork, to match. The angled cut you see in the dark wood allows it to push into the angled "spline" slot cut by the jig.
Do this at both ends, until the wood fits in tightly, then glue it along the whole of the front. It should overhang all round, as it will be sanded back later. This provides protection to the pine box from hands resting on that edge. When the glue is dry, trim the overhang at each end, as for the other splines.
It should also overhang the inside of the box, to provide a "stop" lip for the keyboard, when it is fitted.
Step 10: Feet
I made a set of feet (8 total), from pine stick wood offcuts. These are 24mm square, and a countersunk hole has been put in the middle to sink the screws below the wood. Later, a self-adhesive pad will go over the screw head.
Sand the hard corners off, as shown.
Step 11: Glue Faces to Sides
I added a matching dark wooden "spline" layer to the top of the case. This one has a handle tab cut and sanded into it. The ends are hand-cut/sanded to match the mitre of the box, so it doesn't catch when the box closes.
The clasps were test fitted, to check that these two spline layers have been cut and sanded back smooth enough. Otherwise, the clasp won't sit flush to the surface.
Now the top and bottom can be glued onto the sides. I again used some small double ended pins (veneer pins with heads removed) to locate the sides so they didn't creep. Small blind holes drilled into the top/bottom boards, and the edges of the sides, give a positive lock between the wood pieces while the glue dries.
Once the sides were glued to the bottom, the top was glued on, and all left to dry overnight with a weight on top.
Then the overhanging edges on the top and bottom boards were rough cut back with an X-acto knife, to bring them back to the correct size to match the sides.
Step 12: Adjustments
Some minor adjustments were needed -- the camera spinner module fits tightly into the right-angle corner of the box, but has screw heads that protrude. A small milling tool cleared an area so that the spinner's faces will sit flush to the woodwork.
The two camera and LIRC windows were adjusted a little outward (larger), and then hand bevelled with a file to neaten them up. This is easier to check with the camera spinner mounted, and viewing the resulting image from the Raspberry Pi. If the viewports are not wide enough, they will appear in the picture!
Holes (and a rebate for the diffuser) for the front facing flash were added. It would have been easier to add these while the lid was still un-assembled, but I wasn't sure of exactly where the flash PCB would fit at that point.
Step 13: Sand Into Shape
Once all the cutting and drilling is completed, now it's time to sand everything. The lid, base and sides were sanded flat to remove any pencil marks, glue residue, small dings/scratches, with a Black and Decker mouse sander and vacuum cleaner attachment.
Pay close attention to smoothing up the splines on the corners, to make them neat.
All the corners were then rounded by hand using sand paper in a 5 inch long piece of right-angle wood moulding, as a guide. This will make it easier to stain and clear-coat later, no hard corners!
Step 14: Test Fit
Mounting points for four more feet were added to the rear, so it can be put down on it's back, when the lid is closed.
Friction stays were added to both sides, externally, to keep the display module at the selected angle. The position of the stays was chosen to allow the display to open past 90 degrees to a comfortable viewing angle when fully locked out, but not so far that the unit over-balances!
Step 15: Painting and Staining
To neaten up the inside, all internal woodwork was rough sanded, then painted with a wood primer, undercoat and then sprayed black.
Masking was applied to prevent paint getting into the window/rebates, and the four threaded bush mounting points. Also masking tape was applied to the outer-sides of the box to prevent overspray.
The screen mount panel was also painted in the same way, with masking applied to the logo area (to be glued in later) and the camera/flash windows and diffuser area.
The outside of the box was given a last clean up with isopropyl alcohol, to remove any fingerprints and marks,and then stained with Rustin's Pine stain. The outside logo area was avoided (no masking needed), so that the logo can be glued in after staining.
Step 16: Logo
Once the stain was dry, the logo can be glued in place.
To neaten up the join between the logo and the case, I did one last manual pass with a 2mm diamond tipped engraver to cut a consistent "gully" around it, which was then filled with a mixture of PVA, water, and dark wood dust, run into the gap. Clean up any over-spill quickly!
Step 17: Clear Coats
To protect the outside of the box, all external faces were treated with Rustin's Plastic coat, which dries to a hard, polishable finish. The eight "feet" were also treated separately.
Plastic coat is a two part mix, so I mixed 4 parts of the plastic coating, one part hardener, and two parts thinner, and brushed on one coat every couple of hours. I put four coats over all external faces, before concentrating the next three coats on the logo area to fill in the gaps and protect it further. Do this in a well ventilated area, as the fumes are strong!
Then it was left for 5 days to fully cure off, before going over it all lightly with wetted wet-or-dry paper, to remove any high spots and blemishes. This will partly dull the glossy finish.
I went over it all with 0000 steel wool until it's uniformly dull -- this is messy as it sheds metal particles everywhere. Be sure to fully clean out the box afterwards! A large magnet wrapped in a paper bag is helpful, to pick up all the steel wool fragments/dust for disposal, or an air-blast (outdoors). Or both.
Metal particles and electronics don't mix.
Then, using T-Cut, Silvo or Brasso on a cloth, polish and polish until the shine comes back.
And lastly, using furniture polishing wax, polish it some more, and buff with a clean duster/cloth to get it looking its best!
Step 18: Finishing
Last steps now -- the feet can be screwed on and the felt spots applied to hide the screw heads.
The glass pieces are all stuck into their rebates using silicone sealant. This is a little messy, but covered in part 2 in more detail. Once the sealant is set, clean the glass until it has no smudges on, and no stray sealant within the view port.
The flash diffuser can be stuck in now, and trimmed around -- same milling/PVA and wood dust technique as for the logo.
Step 19: Done!
And that's the box completed.
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